cars78md

I have a 1978 corvette with the L-82 motor. She has the orginal carb.I want to put a holly carb. on her . Do i have to change the intake manifold..

johnt365

If you get a spread bore Holley then no. If you get a square bore Holley you need an adapter plate.

billla

You'd be far better off to have a quality overhaul and tune of your existing carb.

There is zero - zero - power to be gained in the swap, and I think you'll find by the time you sort out all the linkages and stuff you'll be sorry you did it...

jb78L-82

Holley 4175 on my 78 L-82 since 1985-great spreadbore Qjet replacement. Has run flawlessly for all these years. Linkage hooks right up. The fuel line will not hook directly into the 4175 like on the qjet. Much prefer over the qjet. 27 years experience with the 4175!!!!

Vette5.5

Also curious of why you'd want to do something like this. Q-Jets are one of the most sophisticated street carb designs ever made. Because of this, they're generally more difficult to properly set up for engine mods. Can be done though, and well worth the effort. You can throw all sorts of money at trying other things, but bettin' they wont be worth it.

billla

Why?

johnt365

I have read both books by roe and ruggles and all the papers from Grimsrud on the sublect. Its not hard to tune a qjet. Its just easier to tune a holley. And parts more common. What motivated me to switch personally was Lars pointing out that there was little performance difference on a dyno. However the accelerator pump inlet on a q jet is near the center of the bowl unlike the Holley which feeds from the bottom. This made a big difference in starting my car since it may sit for a week or so and helped with hot starts too. In both cases fuel would evaporate or boil out leaving no pump shot for the next start.

I am cheap though and bought 2 holley carbs on craigslist for $50 and then sold one for $50. No risk.

capevettes

I put a spreadbore Holley on my 68 427/390. Pretty simple bolt on. The linkage was pretty straightforward. It felt like I bolted on 50 horsepower. The low and mid range torque improved significantly. Cold starts after sitting for a few days was far better.

Admittedly, I am comparing this to a Q-Jet that was not operating at 100% but there aren't too many people that know what they are doing with these carbs. I have always felt that bolting on a NEW carb is a significant performance improvement. I have had the Holley on the car for about 5 years and it has performed flawlessly

billla

This is kinda the point - comparing a new, healthy carb with one that's 30 years old doesn't really provide a valid comparison.

Unless the engine is going to see a lot of changes, the Q-Jet is a tough carb to beat. It is more difficult to tune, especially given limited parts availability and expertise, but once rebuilt and tuned it will deliver every day. The tiny primaries and huge secondaries are perfect for the street-driven 'Vette.

jb78L-82

Very reliable, has performed great for 27 years, easy to tune, readily available parts, simple to rebuild after 25 years! Power equivalent to the Oem qjet. Mileage slightly worse-difference is very small compared to the qjet!

cars78md

Thanks for all the input.....Am going to keep the q-jet on the vette.....thanks again..

7t9l82

i have used both.the Holley is easier and was quicker until, i put 77 jets in the primary side with smaller rods. drilled out the passages recommended in cliffs book.runs very well. i think the important point is, if you can find a quadrajet that hasn't been ruined.

Priya

Just put a Holley on my AMC Eagle, runs like a brand new fuel injected car. Had one on my 70 Torino and loved it too. Super simple to rebuild as well. My Q-jet runs like crap, I'd put a holley on it if I wasn't planning on converting it to fuel injection.